1. Field of the Invention
The present invention relates to an image forming apparatus that forms an image based on an image signal, including, for example, a printer, a copier, a recording device, and a facsimile apparatus, and relates to a calculation method of a toner consumption amount, and a program.
2. Description of the Related Art
A need exists to accurately detect the toner consumption amount of an image forming apparatus, the purpose of which is to notify the user of the remaining amount of toner, the time for cartridge replacement, and the fee, and to control various image forming process conditions and the toner replenishment amount, based on the toner consumption amount. Examples of methods for detecting the toner consumption amount include a method in which a sensor is provided within a cartridge and a method in which the toner consumption amount is estimated from image data. The former method suffers from the problems of manufacturing cost and detection accuracy. Meanwhile, an example of the latter method is the method proposed by Japanese Patent Laid-Open No. 2012-48056. Japanese Patent Laid-Open No. 2012-48056 proposes a method in which the toner consumption amount is calculated based on a weighting according to the number of consecutive pixels consuming toner and the number of intervals with neighboring pixels.
The toner consumption amount varies depending on the type of image (e.g., screen ruling, character, and photograph). FIGS. 18A and 18B show examples of the toner consumption amounts of images that have the same area ratio (pixel count), but are of different types (character and line image, halftone image (screen ruling: 212 lpi, 141 lpi)). Note that a 212-lpi halftone image is an example of an image having a larger value of screen ruling than that of a 141-lpi halftone image. In particular, FIG. 18A shows toner consumption amounts for an area ratio of 25%. The character and line image has the largest toner consumption amount, the 141-lpi halftone image has the second largest toner consumption amount, and the 212-lpi halftone image has the least toner consumption amount. FIG. 18B shows toner consumption amounts for an area ratio of 50%. The toner consumption amounts are in the order reverse to that of the toner consumption amounts for an area ratio of 25%. More specifically, the character and line image has the least toner consumption amount, the 141-lpi halftone image has the second least toner consumption amount, and the 212-lpi halftone image has the largest toner consumption amount. As can be seen from FIGS. 18A and 18B, the toner consumption amount varies depending on the type of image, and the magnitude relationship between the toner consumption amounts changes depending on the area ratio.
The reason that the toner consumption amount varies depending on the type of image, even when the area ratio is the same, is due to the characteristics of electrophotography. The depth and the extent of an electrostatic latent image vary depending on the dot size or the distance from an adjacent dot even when the area ratio is the same, and thus, the developing performance of toner also varies. As a result, the toner consumption amount changes. Therefore, there is a demand for a method for estimating the toner consumption amount that takes into account the difference between toner consumption amounts depending on the type of image.